System for the control of electric furnaces.



PATENTED JULY 12, 1904 W. MOA. JOHNSON, SYSTEM FOR THE CONTROL OF ELECTRIC FURNACES.

APPLICATION FILED NOV. 18, 1903.

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Y @Wm UNITED STATES Patented July 12, 1904.

PATENT arie VVOOLSEY MoA. JOHNSON, OF LAHARPE, KANSAS.

SPECIFICATION forming partof. Letters Patent No. 764,592, dateqlJu y 12, 1904,

Application filed November 16, 1903. Serial No. 181,316. (No model.)

To all whom it may concern.-

Be it known that I, WooLsEY McA. J oIIN'- 10 electric furnaces, and comprises asuitablepyrometer or other device capable of responding to and indicating temperature changes within the furnace, regulating means for the furnacecircuit, and means connected with the pyrome- 5 ter or indicating device for operating said regulating means.

i 1 will describe my invention as embodied in a pyrometer or indicating device and a regulator of simple construction; but it is to be un- -dersto'od that my invention is not limited to devices of the particular types herein indi-v ,cated as suitable.

For a full understanding of my invention reference is made .to the accompanying draw- 5 ing, in which the figure is a diagrammatic view'of an electric furnace with my'controlling system applied thereto. q

' 1n said'figure the electric furnace 1 is indicated as of the resistance type, the current 3 passing between electrodes2 3 through a body 4 of the material or charge to be treated. It will be understood, however, that-my system is applicable to any type or class of electric furnace.

The furnace is preferably provided with a plurality of openings 5, which are normally V 25. In this position a varlable resistance 26 closed by plugs except when serving for the introduction of the pyrometer. The pyrometer is shown as ofthe Le Chatelier type and 4 comprises concentric cylinders 6 7 of refractory material, such as magnesia or siloxicOn, the end of the outer cylinderbeing sea-led over the open end of the innercylinder. The wires 8 9, which may consist, respectively, of plati- 45 num and of platinum alloyed with ten per cent. of rhodium or of nickel and iron or of other suitable dissimilarmetals, are located within the respective compartments formed by the concentric cylinders and are united by soldering or otherwise at or near the inner 'end of the pyrometer, as indicated at 10. The

outer ends-of said wires are connected to binding-posts upon the pyrometer, and from these binding-posts electrical connection is made to the binding-posts of a suitable galvanolneter 11. -This galvanometer may, if desired, be provided with ascale, which may be conveniently graduatedin degrees of temperatureas determined for the particular instrument. The indicating-needle 12 is preferably of platinum, is insulated from the movable coil 13, and is provided with a metallic contact 14, dipping into mercury 15. A second contact 16., preferably also of platinum, is secured to a movable block 17,'the position of which 6 upon the scale may be adjusted by means of a rack and pinion operated by the milled head )18. The mercury I5 and the movable contact 16 are terminals of an electric circuit which includes a storage battery or other generator 19'and the solenoid 21 of asuitable electro-.- magnetic regulator 20'. Said electromagnetic regulator comprises in the form diagrammatically illustrated a solenoid 21 havinga soft iron core 22, which is adapted to be raised when the circuit is closed through the'solenoid, as will be readily understood. Said core carries a contact 23, which in the position as: sumed by the core whenthe circuit is broken at the galvanometer 11 is adapted to close the circuit through the field 28 of the exciter 29, which furnishes current to the field 30' of the furnace-dynamo 31. When, however, the circuit is closed at the galvanometer, the contact 23 is brought by themovement of the core22 into operative relation with a second contact such other portion as may be found to have a definite temperature relation, thereto. I

preferably introduce the pyrometer into the .1

reacting mass within the chamber at what may i be called its critical point. By'means oi the milled head 18 the adjustable contact 16 is then brought to the point of the galvanorne- 'ter-scale which corresponds to or slightly exvariable resistance 26 and the electromagnetic cut-out 27. These elements maybe of any so constructed and adjusted that the electromagnetic cut-outwill break the circuit only in case the resistance proves insuflicient to quickly reduce the furnace temperature.

It will be understood that it is not essential to employ in connection with my system of control a graduated scale or equivalent means for determining the absolute or relative temperature within the furnace. It is essential merely thata moving element actuated by or constituting apart of the pyrometer shall be capable of bringing into operation a suitable device for regulating or controlling the furnace-circuit. The term indicating device is herein employed to designate an element of this character.

It will be further understood that my invention is not limited to the details of conscribed by way of example.

device connected vice for the furnace-circuit, and means conknown or suitable-type, and are preferably.

I claim 1 1. A system for the control of electric furnaces, comprising a pyrometer, an indicating therewith, a regulating denected with said indicating'device for operating said regulating device, substantially as de-' scribed.

2. A system for the control of electric furnaces, comprising a pyrometer, an adjustable indicating device connected therewith, a regulating device for the furnace circuit, and

'means connected with said indicating device for operating said regulating device, substantially as described. 4

3. In combination, an electric furnace, a portable pyrometer adapted to be inserted therein, an indicating device connected with said pyrometer, a regulating. device for 'the furnace-circuit, and means connected with said indicating device for operating said regulat ing device, substantially as described.

4. In combination, an electric furnace, a portable pyrometer adapted to be inserted therein, an adjustable indicating device connected with said .pyrorneter, -a regulating device for. the furnace-circuit, and means connected with said indicating device for operating' said regulating device, substantially as described. Q

In testimony whereof I aflix my signature in presence of two witnesses.

WOOLSEY MCAQ JOHNSON.

' Witnesses: structlon or circuit connectlons here n de- A. M. EWING, ARTHUR Cox. 

